<?php
/**
 * Created by PhpStorm.
 * User: Administrator
 * Date: 2017/9/20
 * Time: 16:14
 */

$arr = ['13','15','17','18'];
$sb = '18';

//in_array($sb,$arr)
//true 值属于数组中的某个值时，返回true
// false
if (in_array($sb,$arr)){
    echo 'yes';
} else {
    echo 'no';
}